Volcanoes May Have Sparked Life on Earth, Study Says
for National Geographic News
|October 7, 2004|
Before life evolved on Earth, most scientists believe that amino acidsmolecules that are the basic building blocks of lifewere first formed via interactions on Earth or brought to it via collisions with comets and meteorites.
"But how did [the amino acids] form peptides [which are necessary for living cells]? What is the condensing agent?" said Reza Ghadiri, a molecular chemist at the Scripps Research Institute in La Jolla, California. "That is a major problem."
Peptides are chains of amino acids. They form the proteins that are the basis of living cells.
Scientists have had little success in demonstrating a plausible chemical reaction that could have formed peptides on Earth before life existedthe so-called pre-biotic period. In the absence of a plausible chemical reaction, scientists say life could not have evolved via chemical means.
Reporting in tomorrow's issue of the journal Science, Ghadiri and his colleagues demonstrate that a simple volcanic gas, carbonyl sulfide (COS), helps free-floating amino acids to form peptides.
According to Ghadiri, this reaction occurs under a variety of conditions that may have been present on Earth before life evolved. Metal ions, such as iron and lead, and other chemicals intensified the reaction.
"Because there are several ways to do it, it bodes well for pre-biotic conditions," Ghadiri said.
Norman Pace, a molecular biologist and expert on early life at the University of Colorado at Boulder, said the finding is of little surprise.
"All kinds of organic chemistry goes on in volcanic exudates [openings]. Put that volcano on the seafloor [where most volcanism is] and things get even more complex and little explored," he said.
Volcanic Life Origin?
Ghadiri and colleagues Luke Leman, also at Scripps Research Institute, and Leslie Orgel of the Salk Institute for Biological Studies in San Diego, California, embarked on this study as an inquiry to life's origins. Their discovery could be a missing link.
"We can only speculate," Ghadiri said. "But COS is now shown to be a useful and chemically feasible condensing agent."
The authors suggest that since COS decomposes relatively quickly on a geological timescale, it is unlikely to have accumulated to significant concentrations in the atmosphere.
Rather, the authors speculate that the volcanic gas would have influenced amino acids close to sources such as hydrothermal vents on the seafloor, forming peptide chains that would chemically stick to nearby rocks and continue to lengthen.
According to Pace, it is incorrect to infer from the study that life originated at volcanoes. However, Ghadiri said: "It puts the whole idea of pre-biotic speculation on sure footing. It's something that could have happened."
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